# LICENSE HEADER MANAGED BY add-license-header
#
# Copyright 2018 Kornia Team
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

from typing import Union

import torch


class AverageMeter:
    """Computes and stores the average and current value.

    Example:
        >>> stats = AverageMeter()
        >>> acc1 = torch.tensor(0.99) # coming from K.metrics.accuracy
        >>> stats.update(acc1, n=1)  # where n is batch size usually
        >>> round(stats.avg, 2)
        0.99

    """

    val: Union[float, bool, torch.Tensor]
    _avg: Union[float, torch.Tensor]
    sum: Union[float, torch.Tensor]
    count: int

    def __init__(self) -> None:
        self.reset()

    def reset(self) -> None:
        self.val = 0
        self._avg = 0
        self.sum = 0
        self.count = 0

    def update(self, val: Union[float, bool, torch.Tensor], n: int = 1) -> None:
        self.val = val
        self.sum += val * n
        self.count += n
        self._avg = self.sum / self.count

    @property
    def avg(self) -> float:
        if isinstance(self._avg, torch.Tensor):
            return float(self._avg.item())
        return self._avg
